Digital image data captured by a digital camera and acquired by reading a picture and the like using a scanner (hereinafter referred to as “image data”) are variously used as, for example, an output from various types of printers to a recording sheet, etc., and a display to a plurality of monitors connected via the Internet
Such image data are output to a recording sheet, a display, etc., in a visible manner. In some applications, a higher image quality is desired in an output result of the image data. Especially, when image data are output in a commercial application, it is desired that an intended image expression is reproduced on a recording sheet or on a monitor to obtain a higher image quality so that the output result can attract a viewer and appeal to the viewer's emotion.
The high image quality can be formed by complicatedly combining various elements such as clear colors, deep (solid) black color, good graininess, good sharpness, etc. To that end, in order to obtain such high image quality, a high technology is required to adequately adjust various parameters such as contrast, hue, color balance and the like in accordance with the image data. Therefore, a complicated operation may be necessary, which is based on instinct and experience of an operator who performs the image processing.
One aspect of image processing that requires a higher technique is to emphasize or reduce the shine of an object to be imaged having a mirror surface that reflects light, such as a metal or glass. For example, by emphasizing the shine appearance of a vehicle, a watch, a noble metal, a jewel, a dish, pottery, etc., it becomes possible to strengthen the brightness and improve the texture of those objects. On the other hand, for example, by reducing the shine appearance of a glass surface, a water surface, etc., it becomes possible to reduce excessive reflected light by those surfaces, etc., to emphasize a main object to be imaged.
As an example of such an image processing method, there is a proposed method in which by determining gradation change characteristics based on highlight values in and outside a designated area of an image and changing the number of pixels in the designated area, it becomes possible to reproduce a realistic texture of an object including highlight light such metallic luster (see, for example, Patent Document 1). According to the image processing method of Patent Document 1, it becomes possible to perform image processing without the need for complicated operations which rely on an operator's experience.